This invention relates to spectroscopic measurement of magnetic fields, and more particularly to spectroscopic remote sensing of magnetic fields utilizing a gas.
Physicists have long known that magnetic fields that permeate any material alter the electromagnetic spectrum emanating from that material. The magnetic field permeating a material alters the wavelength, polarization, and scattering of the electromagnetic spectrum including altering the index of refraction of the material, all of which can be observed spectroscopically. These phenomena are known as the Zeeman, Hanle, and Faraday effects. Since the magnitude of these effects are directly proportional to the strength of the magnetic field, any of the three effects can be used to derive the magnetic field strength. Astronomers have exploited these phenomena to study astronomical magnetic fields.
Observation of the Zeeman, Hanle, or Faraday effects typically requires a radiance or emission source, a gas, and a magnetic field. Astronomical objects contain all three; a star is made up of glowing gas and magnetic fields. Present methods of detecting man-made or terrestrial magnetic fields use electromotive force (EMF) sensors that react to the magnetic field. Accurately measuring the magnetic fields using present method sensors requires that the sensor either be very close to the area of interest or that the sensor be very large.
The present invention provides a method and system for spectroscopic measurement of magnetic fields that substantially eliminates or reduces at least some of the disadvantages and problems associated with previous methods and systems for measuring magnetic fields.
In accordance with a particular embodiment of the present invention, a method for spectroscopically sensing a magnetic field emanating from an object includes receiving a radiance emission from an object and dispersing the radiance emission into parts of the electromagnetic spectrum. The method also includes detecting a part of the electromagnetic spectrum identified with a selected gas and measuring the magnetic field from a part of the electromagnetic spectrum based on spectral spreading of a spectral line.
The selected gas may comprise a noble gas, such as argon, and dispersing the radiance emission may comprise passing the radiance emission through a prism, diffraction grating or grism.
In accordance with another embodiment of the present invention, a method for spectroscopically sensing a magnetic field emanating from an object includes receiving a radiance emission from an object and polarizing the received radiance emission. The method also includes detecting a part of the electromagnetic spectrum identified with a selected gas from the polarized radiance emission, measuring the polarized radiance emission as a function of frequency and calculating the magnetic field from the polarization measurements. Measuring the polarized radiance emission as a function of frequency may comprise measuring the polarized radiance emission in four Stokes parameters.
Technical advantages of particular embodiments of the present invention include exploitation of the Zeeman, Hanle or Faraday effects to measure terrestrial or manmade magnetic fields. Another advantage includes the use of either direct or reflected solar light as a source for terrestrial or man-made magnetic field measurements. Naturally occurring terrestrial atmospheric gases, molecules or chemicals, such as argon, are exploited for the terrestrial or man-made magnetic field measurements.
Particular embodiments of the invention utilize an argon laser or other laser to illuminate an object for magnetic field measurements. Commercial grade argon gas lasers may be used to illuminate the object to make the magnetic field measurements. A further advantage of the invention is found in the minimal size of the sensor that enables a user to measure a magnetic field with a handheld or airborne sensor.
Other technical advantages will be readily apparent to one skilled in the art from the following figures, descriptions and claims. Moreover, while specific advantages have been enumerated above, various embodiments may include all, some or none of the enumerated advantages.